Skimp on fluids, and your body will release an antidiuretic hormone that leads to water retention that could affect the scale, Dr. Setlzer says. While this sneaky effect is one reason why the scale is a poor measure of body mass loss, you can outsmart it by drinking more—particularly if you fill your glass with water or non-calorie alternatives like unsweetened coffee and tea.
If you do it right, snacks also make a healthy contribution to your weight-loss plan. Keep them snack-size and know ahead of time when you're going to eat them, such as in between lunch and dinner or after dinner. Keep snack calories to 200 or less. Good options include 2 cups of air-popped popcorn tossed with 12 peanuts; a container of nonfat yogurt with 1/2 cup of unsweetened whole-grain cereal; 2 cups of raw veggies such as broccoli, cucumbers and carrots with 1/4 cup of hummus; or 1 tablespoon of almond butter with a small apple.

The researchers hypothesize that participants who abstained from animal products dropped significantly more pounds since plant-based foods include loads of filling fiber and slow-to-digest complex carbs. Though more research is needed to confirm these results, the study authors write, "Vegetarian diets appeared to have significant benefits on weight reduction compared to non-vegetarian diets."

Here’s the full shopping list for exactly what to buy, and check to make sure you have a few pantry staples on hand. Morris recommends starting on a weekend, so you can make a big pot of veggie soup, and give your body a chance to adjust before diving into a busy week. Her plan cuts carbs for the first couple of days, before slowly reintroducing whole grains. And if you want to mix it up, there are lots more options for healthy snacks, just make sure to get a serving of fruit or vegetables, along with protein.